JP4556522B2 - Recording paper and image recording method using the same - Google Patents

Description

  The present invention relates to a recording paper and an image recording method using an ink jet recording method or an electrophotographic recording method using the recording paper.

  The ink jet recording system has been attracting widespread attention because it is easy to color, has low energy consumption, low noise during recording, and can reduce the manufacturing cost of the printer. Furthermore, in recent years, high image quality, high speed, and high reliability have progressed, but there are many opportunities to print on plain paper, and it is extremely important to improve the printability of plain paper.

  In order to improve black character image quality and mixed color bleeding, conventional ink-jet printers use black ink, ink that has low permeability to recording paper that uses pigment as a color material (hereinafter sometimes simply referred to as “paper”). The mainstream is one that uses ink that has a high permeability to recording paper using a dye as a coloring material.

  Therefore, in particular, when printing images with high recording density using color inks that have increased permeability to the paper, curl and undulation occur greatly on the recording paper immediately after printing, and paper jams and images in the printer The rubbing of the part will occur. In addition, when performing double-sided printing, the time required for the curling generated on the recording paper immediately after printing to be relaxed and the time for the ink to dry are required, so that the print productivity is extremely reduced. Further, when an image having a high recording density is printed, there is a problem that curling and waviness that occur after standing and drying are large, and high image quality, curling suppression, and wavy suppression cannot be achieved at a high level.

  In order to improve the curling and undulation after the printing, a method of reducing the curling and undulation by humidifying the paper sheet once and reducing the stress of the paper (for example, refer to Patent Document 1), and the CD direction of the paper A method of reducing curling and undulation by regulating the underwater elongation of the paper (for example, see Patent Document 2), curling the underwater elongation rate in the MD direction and CD direction of the paper by 1.3 times or less, A method for reducing undulation (for example, see Patent Document 3), a method for reducing curling and undulation by setting the underwater elongation in the operation direction of the ink ejection portion to 2.0% or less (for example, see Patent Document 4), A method of reducing curling and undulation by reducing the elongation in water in the CD direction to 1.8% or less (see, for example, Patent Document 5), the pigment contained in the support is 5 to 35% by mass, and a recording sheet ( The internal bond strength of the recording paper is 1 How to reduce the waviness of the coat type ink jet recording sheet by the 0~455g / cm (e.g., see Patent Document 6) have been proposed.

  In the methods described in Patent Documents 1 to 5, it has been reported that curling and undulation are reduced. However, ink that has a high permeability to the inside of the recording paper is used, and the amount of ink discharged is large or the printing speed. However, when the amount of ink ejected per unit time increases rapidly, curling increases, and the document cannot be used.

  In the method described in Patent Document 6, an attempt is made to reduce waviness after printing by keeping the internal bond strength of a recording sheet provided with an ink receiving layer within a certain range. It is not possible to obtain a sufficient effect on curling, undulations, and undulations simply by prescribing. In particular, when ink that has high penetration into the recording paper is used and the amount of ink discharged is large, that is, when the printing speed is high and the amount of ink discharged per unit time is large, the wave is large and used as a document. I can't stand it.

  In addition, in order to improve curling and undulation after standing drying, the irreversible shrinkage rate between the MD direction and the CD direction when the relative humidity of the leaving environment is changed is within a certain range, and thus occurs after standing drying. A method for reducing curling and undulation has been proposed (see, for example, Patent Document 7). However, if the ink penetration of the recording paper is not suppressed, the ink penetrates into the inside of the recording paper when the ink has a high permeability and the amount of ejected ink is large. The absolute amount increases and the curl after standing and drying becomes large, and a sufficient effect cannot be obtained.

On the other hand, in order to improve image quality, a method has been proposed in which an ester nonionic surfactant having an HLB of 11 or more is included in the ink receiving layer (see, for example, Patent Document 8), but this surfactant has high hydrophilicity. Since the hydrophilic group of the base material (base paper) cannot be covered with the hydrophobic group of the surfactant and the amount of ink is large, the recording paper is easily deformed, so the curl is large and cannot be used as a document.
In addition, a method has been proposed in which a surface active agent having an HLB in the range of 3 to 12 is included in the ink receiving layer on the film surface in order to improve the image quality (see, for example, Patent Document 9). Even if it is applied, the amount added is as low as less than 0.1% by mass, the hydrophilic group of the base material cannot be covered with the hydrophobic group of the surfactant, and the amount of ink discharged is particularly quick to penetrate into the recording paper When there is a large amount of ink, that is, when the printing speed is high and the amount of ink ejected per unit time is large, the wave is large and it cannot be used as a document.

In order to prevent curling, a method of size-pressing dry oxidized starch has been proposed (see, for example, Patent Document 10). However, when a large amount of ink is printed, this technique alone can prevent water in the ink. The base material stretches greatly, curls increase, and it cannot be used as a document.
Furthermore, an ink-receiving layer containing silanol-modified polyvinyl alcohol (PVA), 11 to 20% by mass of a nonionic surfactant, and synthetic amorphous silica as a filler has been proposed to improve image quality in the inkjet method. (For example, refer to Patent Document 11) In this method, there is no description of the HLB of the surfactant, and since the HLB of the surfactant used in the examples is 14, the hydrophilicity of the surfactant is low. When applied to paper made of cellulose pulp as a raw material, the hydrophilic group of the substrate cannot be covered with the hydrophobic group of the surfactant. Similarly, this technology alone causes the substrate to be stretched by water in the ink. Large, curl becomes large and cannot be used as a document.

In addition, for printing paper, a method including a bulk softener having an HLB of 6 or less has been proposed to improve bulkiness and flexibility. However, surfactants having an HLB of 6 or less, particularly HLB 4 or less have poor dispersibility, and Since the hydrophilic group cannot be covered with the hydrophobic group of the surfactant, and the absolute amount of stretched and contracted fibers increases, the curl becomes large and a sufficient effect cannot be obtained (for example, see Patent Document 12).
Furthermore, a method has been proposed in which reliability is improved by setting the water retention value of pulp from which recording paper is disaggregated in electrophotography to 80 to 110% and the freeness of 480 to 600 ml (for example, Patent Document 13). In this method, curling in electrophotography can be reduced by controlling the water retention value of the pulp, but paper dust is likely to be generated in electrophotographic printers and copiers due to paper strength reduction. Paper jams may occur due to weakness. In addition, when applied to an ink jet system, when printing and drying, the ink moisture volatilizes and a large curl may occur.

Furthermore, in the ink jet method, a method aimed at stabilizing the shape by impregnating a cellulose cross-linking agent has been proposed (for example, see Patent Document 14). If the amount of binding increases too much, the ink moisture volatilizes when printing and drying, and a large curl occurs. Further, this technique alone cannot cope with paper deformation immediately after printing, and may cause a paper jam in the machine. In addition, when this paper is applied to an electrophotographic copying machine / printer, residual formaldehyde volatilizes in the fixing device, which not only pollutes the inside of the machine but also affects the person who touches the paper.
JP-A-3-38375 JP-A-3-38376 Japanese Patent Laid-Open No. 3-199081 JP 7-276786 A Japanese Patent Laid-Open No. 10-46498 Japanese Patent No. 3172298 Japanese Patent No. 3127114 Japanese Patent Laid-Open No. 10-278409 Japanese Patent Laid-Open No. 62-144986 JP 2002-348798 A JP-A-11-115304 JP 2002-155494 A Japanese Patent Laid-Open No. 9-119091 JP 2002-201597 A

The object of the present invention is to solve the above-mentioned problems of the prior art.
That is, the present invention is capable of double-sided printing by suppressing curling and undulation that occurs immediately after printing when printing by an inkjet recording method, and can suppress curling and undulation that occurs after standing drying, In addition, the unevenness of the image is improved, and even when printing is performed by the electrophotographic recording method, curling and undulation that occurs immediately after printing can be suppressed, and double-sided printing is possible. It is an object of the present invention to provide a recording paper that can be used for both an inkjet recording method and an electrophotographic recording method, and an image recording method using the same.

The inventors of the present invention have intensively studied a method of suppressing curling that occurs immediately after printing on plain paper, imparts double-sided printing suitability by improving waviness, and further suppresses curling that occurs after standing drying.
As a result, the present inventors have confirmed that the curling and undulation that occurs immediately after printing is caused by the rapid elongation of the fiber layer that has absorbed the water in the water-based ink. Also, curling and undulation that occurs after standing drying occurs due to shrinkage due to dehumidification of the fiber layer that has absorbed the ink, and further, ink penetration in a minute time in the thickness direction of the paper is fast, and ink penetration is deep. It was confirmed that curling and undulation after standing drying increased.

  Based on these results, the present inventors have eagerly studied the stretching / transmitting property of the fiber layer that has absorbed the ink due to water absorption and desorption. As a result, it can be seen that the stretch and transmission properties due to moisture absorption and desorption are closely related to the expansion and contraction rate of the paper. Decreasing the stretch rate weakens the stretch and transmission properties, and curls, wavy and left to dry immediately after printing It has been found that curling and undulation that occurs later can be reduced. In order to reduce the stretch ratio, a surfactant having a certain range of HLB and / or a substance having one reactive group that reacts with a carboxyl group or an active hydrogen group of a hydroxyl group is present on the paper surface and / or inside, It has been found that by covering the hydroxyl groups of paper cellulose with these, the formation of hydrogen bonds is hindered and the expansion / contraction rate is reduced, thereby reducing the curl and wave.

In addition, the present inventors, in particular, curl and waviness that occur after standing and drying, when the fibers that have absorbed water in the water-based ink are dried, the interfiber bonds are freely reconstructed, and only the portion where the ink has permeated. It was confirmed that shrinkage curl was generated from the original dimensions.
From these results, the present inventors have eagerly investigated the dimensional stability of the fiber layer that has absorbed the ink by dehumidification of water. As a result, it can be seen that there is a deep relationship between the formation of bonds other than hydrogen bonds between fibers and the dimensions before and after printing, and by leaving bonds between the fibers other than hydrogen bonds that are not cut by water, they are left to dry. By treating the paper with a material capable of reacting with hydroxyl groups of paper cellulose, it is possible to reduce the curl and undulation that occurs later, and to stabilize the dimensions, so that bonds other than hydrogen bonds are formed between the fibers. It was found that the curl and wave formed after being dried in the fiber were reduced.

  Further, when the surface sizing agent, which is an essential component of the paper, and the curl reducing material are simultaneously processed on the paper, a surfactant having a certain range of HLB that particularly affects paper deformation immediately after paper output and / or Alternatively, a substance having one reactive group that reacts with an active hydrogen group of a carboxyl group or a hydroxyl group and a material capable of reacting with a hydroxyl group of paper cellulose that has a particular effect on paper deformation after leaving the paper output are added simultaneously. This makes it difficult for the surface sizing agent to inhibit the effect of reducing the dimensional change of each material. As a result, curling that occurs immediately after printing, curling that occurs after leaving and drying, and curling that occurs after drying can be dramatically reduced. I found out.

  In addition, electrophotographic recording copiers and printers can also reduce curling and waviness by using papers to which the technology of the present invention is applied, as well as improving paper strength and reducing paper jams. It has been found that even when coexisting with a surface sizing agent, the effect is not reduced, so that a dramatic effect can be obtained such that generation of paper dust is suppressed.

  On the other hand, regarding the image quality, in the ink jet recording method, in addition to the above-described technique, a nonionic surface active agent is added to reduce curl by allowing a cationic material that is ionic opposite to the ink or the ink dispersant to be present on the paper. The color developability which is lowered by the agent can be improved. Further, in order to ensure image transferability in the electrophotographic system, the electrical resistance characteristic of the paper is important. In particular, in the present invention, since a surfactant or a cationic material that may change electrical characteristics is added, the range for securing image transferability in an electrophotographic system is studied, and a stable image can be obtained. We have found a range of electrical characteristics that can be transferred, and have developed paper that can be used for both electrophotographic and inkjet systems.

That is, the present invention is <1> using at least cellulose pulp as a raw material , one selected from monoglycidyl ether having one reactive group that reacts with a carboxyl group and an active hydrogen group of a hydroxyl group, and / or HLB of 6 or more and less than 11 Nonionic surfactant in a range of 0.05 to 1.5 g / m ² and further having two or more reactive groups that react with active hydrogen groups such as carboxyl groups and hydroxyl groups, ammonium zirconium carbonate, polycarbodiimide and poly One or more selected from glycidyl ether is contained in the range of 0.03 to 1.0 g / m ² , the water retention value C of the paper represented by the following formula (1) is in the range of 50 to 100%, The recording paper is characterized in that the wet tensile strength residual ratio R in the CD direction of the paper represented by the following formula (2) is in the range of 5 to 20%.
Water retention value C (%) = {(A−B) / B} × 100 Formula (1)
Residual ratio of wet tensile strength in CD direction R (%) = (Sw / S) × 100 Formula (2)

  In the above formula (1), A represents the mass (g) of the wet paper piece after centrifugal dewatering, and B represents the absolute dry mass (g) of the paper. In the above formula (2), Sw represents wet tensile strength (kN / m) and S represents dry tensile strength (kN / m).

<2>Young's modulus (N / mm ² ) × [thickness (mm)] ³ is in the range of 2.0 to 10.0 N · mm, and the air permeability is in the range of 10 to 100 s. It is a recording paper as described in <1>.

< 3 > Using at least cellulose pulp as a raw material, the water retention value C of the paper represented by the above formula (1) is in the range of 50 to 100%, and the paper represented by the above formula (2) is wet in the CD direction. a tensile strength recording paper residual rate R is in the range of 5-20%, a record sheet you characterized by being obtained by applying the thermosetting material and / or thermoplastic material.

< 4 > The recording paper according to < 3 >, wherein an application amount of the thermosetting material and / or the thermoplastic material is in a range of 0.5 to 5.0 g / m ² .

< 5 > An ink jet recording type image recording method for ejecting ink droplets onto a recording sheet and recording an image on the surface of the recording sheet,
The image recording method is characterized in that the recording sheet is the recording sheet described in <1>.

< 6 > A charging step for charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and a surface formed on the surface of the electrostatic latent image carrier. Developing the electrostatic latent image using an electrostatic latent image developer to form a toner image, transferring the toner image to the surface of the recording paper, and fixing the toner image on the surface of the recording paper An electrophotographic image recording method including a fixing step,
The image recording method is characterized in that the recording sheet is the recording sheet described in <1>.

  According to the present invention, when printing is performed by an ink jet recording system, double-sided printing is possible by improving the image quality of a document and suppressing curling and undulation that occurs immediately after printing. In addition, it is possible to provide a recording paper that does not cause defective image transfer even when an image is formed by an electrophotographic method and can be used for both ink jet and electrophotographic methods, and an image recording method using the same. .

Hereinafter, the present invention will be described in detail by roughly dividing it into a recording sheet and an image recording method.
<Recording paper>
The recording paper of the present invention is composed of at least cellulose pulp as a raw material , one selected from monoglycidyl ether having one reactive group that reacts with a carboxyl group and an active hydrogen group of a hydroxyl group, and / or HLB of 6 or more and less than 11 Zirconium ammonium carbonate, polycarbodiimide, and polyglycidyl containing a nonionic surfactant in the range of 0.05 to 1.5 g / m ² and having two or more reactive groups that react with active hydrogen groups such as carboxyl groups and hydroxyl groups One or more selected from ether is contained in the range of 0.03 to 1.0 g / m ² , the water retention value C of the paper represented by the following formula (1) is in the range of 50 to 100%, and The wet tensile strength residual ratio R in the CD direction of the paper represented by the following formula (2) is in the range of 5 to 20%.
In the present invention, the substance having one reactive group is one selected from monoglycidyl ether. The substance having two or more reactive groups means one or more selected from ammonium zirconium carbonate, polycarbodiimide, and polyglycidyl ether.

Water retention value C (%) = {(A−B) / B} × 100 Formula (1)
Residual ratio of wet tensile strength in CD direction R (%) = (Sw / S) × 100 Formula (2)
In the above formula (1), A represents the mass (g) of the wet paper piece after centrifugal dehydration, and B represents the absolute dry mass (g) of the paper. In the above formula (2), Sw represents wet tensile strength (kN / m), and S represents dry tensile strength (kN / m).

  The recording paper of the present invention having the above characteristics can be printed on both sides by suppressing curling and undulation that occurs immediately after printing when printing is performed using an ink jet recording system using the recording paper. (2) Curling and undulation after standing drying can be suppressed. (3) Since the paper strength immediately after printing can be maintained, it is possible to output without paper jam in the output machine.

  In addition to this, when printing is performed by an electrophotographic method, (4) curling and undulation that occurs immediately after printing can be suppressed, and (5) curling and undulation that occurs after standing drying can be suppressed. (6) Since paper strength can be maintained, not only paper can be output without jamming in the output machine, but also surface sizing agents can be used frequently, so that the generation of paper dust can be reduced and related troubles can be suppressed. Can do. That is, it has been found that satisfying the conditions of the above formulas (1) and (2) makes it possible to suppress curling and undulation after printing and maintain paper strength.

  On the other hand, in the paper used in the conventional ink jet recording system and electrophotographic recording system, the water retention value C as defined in the present invention is in the range of 100% or more, so the curl becomes large and the beating is weakened. For example, when the water retention value is less than 100%, the wet tensile strength residual ratio R as defined in the present invention is less than 5% and curl is reduced, but the paper strength immediately after printing cannot be maintained. Paper jam occurs in the output machine or paper dust is likely to be generated, and paper dust accumulates in the output machine, and related troubles are likely to occur.

  Also, the conventional paper usually has a wet tensile strength residual ratio R of less than 5%, and when it is increased to 5% or more with a wet paper strength enhancer or the like, the water retention value becomes 100% or more, and hydrogen bonding between fibers. The amount of curl increases and the curl immediately after printing is extremely large, causing paper jams in the output machine. To reduce curl immediately after printing and after printing dry and to suppress troubles in the machine. I could not.

First, the characteristic values used in this patent will be described.
The water retention value of the recording paper in the present invention is the JAPAN TAPPI No. 26: 2000 (measured by changing the conditions). Specifically, the condition was changed by immersing a piece of paper cut into 1 cm × 1 cm equivalent to 0.5 g of absolute dry for 10 minutes instead of a pulp suspension equivalent to 0.5 g of absolute dry as a sample. As a method of using and centrifuging, the paper piece was placed in a metal cup filter so as not to be biased and set in a centrifugal sedimentation tube. Other procedures and conditions are described in JAPAN TAPPI No. 26: 2000.

The water retention value C was calculated by the following formula (1).
Water retention value C (%) = {(A−B) / B} × 100 Formula (1)
In the above formula (1), A is the mass (g) of the wet paper piece after centrifugal dehydration, and B is the absolute dry mass (g) of the paper.

Further, the wet tensile strength residual ratio R in the CD direction in the present invention is determined by the following formula (2) by a measuring method according to JIS P 8135 (partially limited or changed).
Residual ratio of wet tensile strength in CD direction R (%) = (Sw / S) × 100 Formula (2)
In the above formula (2), Sw represents wet tensile strength (kN / m), and S represents dry tensile strength (kN / m).

  As the partially limited or changed conditions, the tensile strength was measured using a vertical tensile method (JIS P 8135 7.2.1), and the wet tensile strength Sw was measured with respect to the length of the immersed portion of the test piece. The nonionic surfactant Surfynol 465, which is a penetration accelerator, has a thickness of 30 mm, an immersion time of 10 seconds, and an immersion liquid as a solution having characteristics close to that of ink that is actually printed by ink jet rather than water. This is that an aqueous solution of 2% by mass (made by Nissin Chemical Industry Co., Ltd.) with respect to deionized water was used, and after dipping, excess water was absorbed with a Kimwipe and the tensile strength was measured. The tensile strength S in a dry state is measured without allowing the test piece to stand overnight in an environment of 23 ° C. and 50% RH and does not penetrate into the liquid. Both were measured in an environment of 23 ° C. and 50% RH. Other procedures and conditions are the same as JIS P 8135.

  Note that the reason why the immersion liquid was measured with a characteristic particularly close to ink as described above is that the relationship with the actual curl is higher than when water is used. The “CD (direction)” is a direction crossing the flow direction at the time of recording paper manufacture, and when measuring the tensile strength of the recording paper, the dimension in the direction crossing the flow direction at the time of recording paper manufacture is set. It was measured.

  As described above, the water retention value C in the present invention needs to be in the range of 50 to 100%, preferably in the range of 60 to 90%, and more preferably in the range of 70 to 85%. When the water retention value C is less than 50%, the water retention property is too low, and when ink-jet printing is performed, the water absorption is inferior, so that ink bleeding tends to occur. On the other hand, if it exceeds 100%, curling will increase and paper jam will occur in the output machine.

  The wet tensile strength residual ratio R in the present invention needs to be in the range of 5 to 20%, preferably in the range of 8 to 17%, and more preferably in the range of 10 to 15%. When the wet tensile strength residual ratio R is less than 5%, the strength when the ink penetrates is too low, and paper jam occurs in the output machine when printing is performed by the ink jet method. In addition, the curl after printing is large and it is difficult to withstand use as a document. On the other hand, if it exceeds 20%, the amount of binding between the cellulose fibers of the paper becomes large, especially the curl immediately after printing becomes large, and a paper jam occurs in the output machine.

Furthermore, in the present invention, among recording papers satisfying the ranges of the water retention value C and the wet tensile strength residual ratio R, Young's modulus (N / mm ² ) × [thickness (mm)] ³ is 2.0 in particular. Recording paper having a range of ˜10.0 N · mm and an air permeability of 10 to 100 s is preferable.

Specifically, first, when the water retention value is reduced from a value exceeding the normal value of 100% to the range specified in the present invention, the Young's modulus of the recording paper is improved, and in particular, the Young's modulus (N / mm ² ). X [Thickness (mm)] It was found that curling is greatly reduced by setting ³ to a range of 2.0 to 10.0 N · mm.

The Young's modulus (N / mm ² ) × [thickness (mm)] ³ is preferably in the range of 2.5 to 7.5 N · mm, and more preferably in the range of 2.5 to 5.0 N · mm. If it is less than 2.0 N · mm, the recording paper will not be sufficiently stiff, and curling reduction may not be achieved immediately after printing or after standing and drying. On the other hand, if it exceeds 10.0 N · mm, the stiffness is too high, which not only causes a problem in conveyance in the image recording apparatus, but may also cause a problem with the texture of the paper.
The Young's modulus of the recording paper is obtained by measuring the tensile elastic modulus in the CD direction of the paper according to the method of JIS P8113.

  Furthermore, with regard to the air permeability, when the air permeability increases, color mixing blur tends to occur after printing, and as a result of examination, it has been found that color mixing blur occurs when the air permeability exceeds 100 s. It has been found that when the air permeability is in the range of 10 to 100 s, the occurrence of color mixing blur can be suppressed without impairing other characteristics.

The air permeability is preferably in the range of 10 to 50 s, and more preferably in the range of 10 to 30 s. If the air permeability is less than 10 s, when the paper feeding mechanism uses vacuum in the electrophotographic copying machine / printer, the vacuum feeds a plurality of sheets simultaneously. On the other hand, if it exceeds 100 s, the ink does not penetrate immediately after printing as described above, and color mixing blur occurs.
Here, the air permeability refers to J Tappi No. 5. Oken type air permeability.

Next, the configuration of the recording paper of the present invention will be described.
As described above, in order to reduce the curling and undulation of the recording paper after ink printing, it was necessary to reduce the amount of inter-fiber hydrogen bonding in the base paper. In this case, weakening the beating, etc. The water retention value C can be reduced to less than 100%, but at the same time, the paper strength is greatly reduced, and paper jams occur in the output machine or paper dust is likely to be generated. As a result, paper dust accumulates in the output machine, and troubles are likely to occur. Further, when polyacrylamide or the like is used to improve the wet strength, the water retention value C increases and the curl increases, so that paper jam occurs in the output machine, and the paper is reduced while curling is reduced. In other words, there is no recording paper that can maintain both strengths, that is, a recording paper that satisfies the water retention value C and the wet tensile strength residual ratio R within the range defined in the present invention.

  More specifically, the hydroxyl group in the material constituting the recording paper is usually such that the hydroxyl group forms a hydrogen bond with each other (via water molecules or without water molecules), The bond distance expands and contracts due to a change in the amount of water due to ink permeation / drying during printing, which is unstable. Such instability of the coupling is considered to cause a dimensional change of the recording paper on a macro scale, and finally to curl and waviness.

  For example, a recording paper used in a conventional ink jet recording method is unstable because the hydrogen bond formation is not inhibited by the material contained in the recording paper, and the number of hydrogen bonds is not suppressed. The dimensional change due to expansion / contraction, dissociation, and recombination of bonds could not be prevented, and the above-described properties (1) to (3) could not be achieved at a high level. In addition, a method of filling between the fibers can be considered to inhibit the formation of hydrogen bonds, but in this case, there is a concern that the filling may inhibit the ink from being absorbed into the recording paper and cause bleeding.

  As a result of intensive studies by the present inventors, the dimensional change caused by the hydroxyl group is caused by bonding various materials described later to the material (fiber) constituting the recording paper, or by reacting / crosslinking to inhibit interfiber bonding. It has been found that an excellent effect of finally preventing the occurrence of curling and undulation can be obtained by suppressing the dimensional change of the recording paper without forming a free hydrogen bond.

Specifically, a recording sheet satisfying the above characteristics can be obtained by the following two methods.
The first method comprises at least 0.05 to 1.5 g / min of a substance having one reactive group that reacts with a carboxyl group or an active hydrogen group of a hydroxyl group and / or a nonionic surfactant having an HLB of 6 or more and less than 11. This is a method of applying to a sheet in the range of m ² .
That is, the recording paper of the present invention comprises a nonionic surfactant having one or more selected from the above-mentioned substances having one reactive group that reacts with an active hydrogen group of a hydroxyl group and / or an HLB of 6 or more and less than 11. , 0.05 to 1.5 g / m ² .

  Here, the “applied to paper” means that a material having the above characteristics is added by internal addition and / or coating (surface treatment) when producing a recording paper, and between the pulp fibers inside the recording paper. This refers to bonding and bonding materials. Thus, by providing a specific material, the coupling | bonding between fibers can be inhibited as mentioned above.

  The HLB of the nonionic surfactant in the present invention (hereinafter sometimes simply referred to as “surfactant”) is preferably in the range of 6 or more and less than 11, more preferably in the range of 7-9. When the HLB exceeds 11, the hydrophilicity is high, the cellulose coating effect of the surfactant in the substrate is low, and the effect of reducing the dimensional change of the recording paper by the surfactant is low. Later curling and undulation may be increased. If the HLB is less than 6, the surfactant dispersibility is low, the surfactant cannot be uniformly present on the paper, and the effect of reducing the dimensional change by the surfactant is low. In some cases, curling and undulation after drying may increase.

Nonionic surfactants used in the present invention include, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester Acetylene glycol ethylene oxide adduct, polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, polyethylene glycol polypropylene glycol block copolymer, glycerin ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, and the like can be used.
Among these, acetylene glycol ethylene oxide adduct is particularly preferable.

Examples of the substance having one reactive group that reacts with the carboxyl group and the active hydrogen group of the hydroxyl group include monoglycidyl ether, trimethylsilylating agent, acetic anhydride, and chromium-based water repellent. Of these, monoglycidyl ether is preferably used.
Examples of the monoglycidyl ether include Allyl Glycidyl Ether, 2-Ethylhexyl Glycidyl Ether, Phenyl Glycidyl Ether, Phenol (EO) ₅ Glycylyl Ether (EO represents ethylene oxide), p-tert-butyl ether glyceryl ether. Butyl glycidyl ether, cresyl glycidyl ether, butoxypolyethylene glycol monoglycidyl ether, and the like can be used. Moreover, chlorosilane, alkoxysilane, silazane, etc. can also be used as a trimethylsilylating agent. Moreover, you may use acetic anhydride as an esterifying agent. Of these, butoxypolyethylene glycol monoglycidyl ether is particularly preferred.

In the present invention, the amount of the surfactant and / or the substance having one reactive group that reacts with the active hydrogen group of the carboxyl group or hydroxyl group needs to be in the range of 0.05 to 1.5 g / m ^2. There, more preferably in a range of 0.1~1.2g / m ^2, more preferably in the range of 0.2 to 1.0 g / m ^2.

If the amount of the surfactant or the like is less than 0.05 g / m ² , the amount of the surfactant is small, so that the cellulose coating effect in the base material by the surfactant or the like is low, and the dimensional change reduction effect of the recording paper is reduced. The curl and undulation may increase. On the other hand, if the amount exceeds 1.5 g / m ² , the amount of the surfactant and the like is too large and the water retention becomes low and the water absorption is poor. Problems can occur.

In the present invention, in order to reduce curl and cockle immediately after printing, in addition to the surfactant and / or the substance having one reactive group that reacts with the carboxyl group and the active hydrogen group of the hydroxyl group, a carboxyl group is further added. It is necessary to provide a substance having two or more reactive groups that react with an active hydrogen group such as a group or a hydroxyl group in the range of 0.03 to 1.0 g / m ² . Thereby, the wet tensile strength residual ratio R can be stabilized more in the range.

That is, the present invention provides the wet tensile strength by adding a substance having two or more reactive groups that react with an active hydrogen group such as a carboxyl group and a hydroxyl group in the range of 0.03 to 1.0 g / m ^2. The residual ratio can be kept in the range of 5 to 20%, especially curling after printing is dried, and further, by using both methods at the same time, curling can be reduced while maintaining the strength of the paper, Since a certain amount of the surface sizing agent can be used simultaneously, the generation of paper dust can also be reduced.

Examples of the substance having two or more reactive groups that react with active hydrogen groups such as carboxyl group and hydroxyl group include polycarboxylic acid resin, melamine resin, glyoxal resin, water-soluble urethane resin, ammonium zirconium carbonate, polycarbodiimide, Glycidyl ether or the like can be used.
Among these, ammonium zirconium carbonate, polycarbodiimide, and polyglycidyl ether are particularly preferable, and any one or more of these can be used.

As described above, the amount of the substance having two or more reactive groups that react with an active hydrogen group such as a carboxyl group and a hydroxyl group needs to be in the range of 0.03 to 1.0 g / m ² . A range of 05 to 0.9 g / m ² is more preferable, and a range of 0.1 to 0.8 g / m ² is more preferable. If the applied amount is less than 0.03 g / m ² , since the amount is small, the amount of bonds other than hydrogen bonds between celluloses is small, and the strength retention effect and wetness suppression effect of the recording paper are reduced, curling and corrugation May become larger. On the other hand, if it exceeds 1.0 g / m ² , the amount is too large and the amount of bonds between the cellulose fibers of the paper increases too much, and curling and undulation may increase.

The second method for obtaining the recording paper of the present invention uses at least cellulose pulp as a raw material, the water retention value C of the paper represented by the above formula (1) is in the range of 50 to 100%, and the above formula ( In this method, the wet tensile strength residual ratio R in the CD direction of the paper represented by 2) is in the range of 5 to 20%, and a thermosetting material and / or a thermoplastic material is applied to the paper. The application is the same as in the first method, and as a result, binding between fibers can be inhibited as described above.

  The thermoplastic material is a material constituting the recording paper, for example, pulp fibers contained in the base paper, and the material is plasticized and bonded by heat at the time of drying when manufacturing the recording paper. It is a substance that plays a role and can form an adhesive state that does not easily dissociate in the presence of water. The thermosetting material is a material that constitutes recording paper, for example, pulp fibers contained in the base paper, and is subjected to a thermosetting reaction by heat at the time of drying when the recording paper is produced, and easily in the presence of water. It forms a bond that does not dissociate, reacts with a reactive functional group containing hydrogen, such as a hydroxyl group, to form a covalent bond that does not dissociate easily in the presence of water, or polymerizes itself. It is a material that does not easily change its form. The thermosetting material is more preferably a cross-linking agent (a material having two or more reactive groups capable of forming a covalent bond with other molecules) capable of cross-linking materials constituting the recording paper.

  The thermosetting material is not particularly limited as long as it is cured by heat and crosslinks and bonds the fibers, but a material having a curing temperature in the range of 50 to 150 ° C. is preferable.

Examples of the thermosetting material include thermosetting resins such as formaldehyde resin, phenol resin, melamine resin, and polycarbodiimide resin. Moreover, the epoxy resin and zirconium ammonium carbonate which bridge | crosslink fibers may be sufficient. Further, it may be an aqueous polyurethane resin that is polymerized and cured.
In addition, as a thermosetting material, a foaming thing is more preferable.

  The thermoplastic material is not particularly limited as long as it is plasticized by heat and bonds fibers together, but a material having a softening temperature in the range of 50 to 150 ° C is preferable.

Examples of the thermoplastic material include thermosetting resins such as polyester resin, polyethylene, polypropylene, and vinyl acetate.
The thermosetting material and thermoplastic material in the present invention are not limited to the materials listed here, as long as they have a function of bonding and crosslinking fibers.

The method of applying the thermosetting material and / or the thermoplastic material to the paper is particularly preferable as a method that satisfies the above-mentioned preferred range regarding the Young's modulus (N / mm ² ) × [thickness (mm)] ³ and air permeability. In this case, the applied amount is preferably in the range of 0.5 to 5.0 g / m ² , and more preferably in the range of 1.0 to 3.0 g / m ² in terms of dry mass per recording paper. .

When the content (applied amount) of the thermoplastic material / thermosetting material in the recording paper is less than 0.5 g / m ² , the Young's modulus (N / mm ² ) × [thickness (mm)] ³ is 2. It is less than 0.0, and curling and undulation may not be sufficiently suppressed. On the other hand, if it exceeds 5.0 g / m ² , the air permeability exceeds 100 s, the ink permeability of the recording paper is lowered, and when different color inks are applied adjacent to the surface of the recording paper, Bleeding may occur between the two.

  The recording paper of the present invention is made from at least cellulose pulp, and a substance having one reactive group that reacts with the surfactant and / or carboxyl group or active hydrogen group of the hydroxyl group in the following substrate, or Thermosetting materials and / or thermoplastic materials added internally, those treated with a surface sizing agent on the surface thereof, or those coated with the material on the surface of the base paper, etc. Or there is no restriction | limiting in particular if it is contained by coating (surface treatment).

The base material is made of at least cellulose pulp, and may be the following base paper, or plain paper obtained by treating the base paper surface with a pigment or a binder.
The base paper contains cellulose pulp, but known cellulose pulp can be used, specifically chemical pulp, more specifically hardwood bleached kraft pulp, hardwood unbleached kraft pulp, conifer bleached kraft. Pulp, softwood unbleached kraft pulp, hardwood bleached sulfite pulp, hardwood unbleached sulfite pulp, softwood bleached sulfite pulp, softwood unbleached sulfite pulp, wood, and fiber raw materials such as cotton, hemp, and leather The produced pulp can be used.

  In addition, ground wood pulp that mechanically pulped wood and chips, chemimechanical pulp mechanically pulped after soaking chemicals into wood and chips, and pulp with a refiner after the chips are digested until they are slightly soft Thermomechanical pulp that has been made into a material can be used. These may be used only with virgin pulp, or waste paper pulp may be added as necessary.

  In particular, pulp used in virgin is bleached mainly using ozone / hydrogen peroxide without using chlorine gas and without using chlorine dioxide (Elementary Chlorine Free; ECF) or chlorine compounds. It is preferably one that has been bleached by a method (Total Chlorine Free; TCF).

  In addition, as a raw material of the waste paper pulp, there are unprinted waste paper such as cuts, damaged paper, widened white, special white, medium white, white loss generated in bookbinding, printing factories, cutting offices, etc .; Used high-quality paper, high-quality coated paper, etc .; high-quality printed old paper; water-based ink, oil-based ink, old paper written with pencils, etc .; printed high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, etc. Newspaper waste paper containing medium; waste paper such as medium-quality paper, medium-quality coated paper, and reprint paper;

  The waste paper pulp used for the base paper used in the present invention is preferably one obtained by treating the waste paper raw material with at least one of ozone bleaching treatment and hydrogen peroxide bleaching treatment. Moreover, in order to obtain a base paper with higher whiteness, it is desirable that the ratio of the used paper pulp obtained by the bleaching treatment is 50% by mass or more and 100% by mass or less. Furthermore, from the viewpoint of resource reuse, it is more preferable that the ratio of the used paper pulp is 70% by mass or more and 100% by mass or less.

  The ozone treatment has an action of decomposing a fluorescent dye or the like usually contained in fine paper, and the hydrogen peroxide treatment has an action of preventing yellowing due to alkali used during deinking treatment. In particular, it is known that the combination of the two not only facilitates deinking of waste paper, but also improves the whiteness of the pulp. Moreover, since it also has an action of decomposing and removing residual chlorine compounds in the pulp, it has a great effect in reducing the content of organic halogen compounds in the waste paper using chlorine bleached pulp.

  Moreover, in order to adjust opacity, whiteness, and surface property, it is preferable to add a filler to the base paper used for this invention. In particular, when it is desired to reduce the amount of halogen in the paper, it is preferable to use a filler that does not contain halogen. Usable fillers are heavy calcium carbonate, light calcium carbonate, chalk, kaolin, calcined clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, aluminum silicate, calcium silicate, magnesium silicate And white inorganic pigments such as synthetic silica, aluminum hydroxide, alumina, sericite, white carbon, saponite, calcium montmorillonite, sodium montmorillonite, bentonite, and organic pigments such as acrylic plastic pigment, polyethylene, urea resin, etc. Can do. Moreover, when mix | blending waste paper, it is necessary to estimate the ash content contained in a waste paper raw material previously, and to adjust addition amount.

  Furthermore, it is preferable to add an internal sizing agent to the base paper used in the present invention. As the internal sizing agent, a neutral rosin-based sizing agent used for neutral papermaking, alkenyl succinic anhydride (ASA). Alkyl ketene dimer (AKD) and petroleum resin sizing agent can be used.

  In addition, when the surface of the recording paper is adjusted to be cationic, for example, a hydrophilic cationic resin can be treated on the surface as the cationic substance. In order to suppress this, it is preferable that the paper size before applying the cationic resin is 10 seconds or more and less than 60 seconds.

The recording paper of the present invention can be obtained by subjecting the base paper as described above to surface treatment with, for example, a surface sizing liquid containing the surfactant or the like.
The surface sizing liquid is mainly composed of a solvent such as water, and the concentration of the surface sizing agent and nonionic surfactant contained therein is preferably in the range of 1 to 10% by mass, and 3 to 7% by mass. A range is more preferable.

The application amount of the surface size liquid is preferably in the range of 0.1 to 3.0 g / m ² and more preferably in the range of 1.0 to 2.0 g / m ² per one side of the recording paper. .
When the treatment amount (applied amount) exceeds 3.0 g / m ² , the absolute amount of the surface sizing agent is large, the curling reduction effect of the surfactant or the like is inhibited, and curling and undulation may be increased. On the other hand, when the amount is less than 0.1 g / m ² , the absolute amount of the surface sizing agent is small, and the pigment applied together with the surface sizing agent cannot be fixed on the surface of the base paper. In some cases, a large amount of paper dust is generated, causing trouble to the machine.

  Specifically, as the surface sizing agent, among the surface sizing agents, it is preferable to use not only oxidized starch usually used as a surface sizing agent, but also acetylated starch and phosphate esterified starch with improved hydrophobicity. . Also, polyvinyl alcohol having a very low saponification degree to leave a hydrophobic group or a very high saponification degree to improve the crystallinity and improve the hydrophobicity is preferably used. Further, for the purpose of improving the image quality in the ink jet system, a polyvinyl alcohol having a low polymerization degree may be used. Furthermore, a silanol-modified surface sizing agent with improved hydrophobicity may be used. Moreover, these may be mixed or used alone.

The surface treatment is carried out by applying the surface sizing liquid to the paper by a commonly used application means such as a size press, shim size, gate roll, roll coater, bar coater, air knife coater, rod blade coater, blade coater. be able to. Thereafter, the recording paper of the present invention can be obtained through a drying process.
In the present invention, the addition of the surfactant or the like to the paper may be performed not only by the treatment with the surface sizing agent but also by, for example, mixing and adding a surfactant or the like during papermaking.

The basis weight of the recording paper of the present invention is not particularly limited, preferably in a range of 60~128g / m ^2, more preferably in the range of 60 to 100 / m ^2, of 60 to 90 g / m ² Within the range is more preferable. A higher basis weight is more advantageous for curling and waving, but if the basis weight exceeds 128 g / m ² , the paper becomes too stiff and the paper runnability of the printer may be reduced. On the other hand, if it is lower than 60 g / m ² , it may be difficult to suppress the occurrence of curling and undulation, and it is not preferable from the viewpoint of set-off.

Further, it is preferable to adjust the fiber orientation ratio in the range of 1.0 to 1.55, preferably in the range of 1.0 to 1.45, more preferably in the range of 1.0 to 1.35 during papermaking. . By adjusting in this way, curling of the paper (recording paper) after printing by the inkjet method can be reduced. The fiber orientation ratio is the fiber orientation ratio determined by the ultrasonic propagation velocity method, and the ultrasonic propagation velocity in the MD direction of the paper (traveling direction of the paper machine) is defined as the CD direction of the paper (perpendicular to the traveling direction of the paper machine). ) Divided by the ultrasonic wave propagation velocity, and is represented by the following equation.
Fiber orientation ratio (T / Y ratio) = (MD direction ultrasonic propagation speed) / (CD direction ultrasonic propagation speed)
In addition, the fiber orientation ratio by this ultrasonic propagation velocity method is measured using SonicSheetTester (manufactured by Nomura Corporation).

  The recording paper of the present invention preferably contains a cationic polymer or a polyvalent metal salt on its surface. When the surface of the recording paper contains a cationic polymer or a polyvalent metal salt, when the ink for inkjet contains an anionic polymer, cross-linking the ink enables extremely quick aggregation of the coloring material and is excellent. Since it is thought that the printing image quality is obtained and the penetration of the ink solvent into the paper is suppressed, it is possible to further improve the curling and undulation that occurs immediately after printing, and further the occurrence of curling and undulation after standing drying. .

  Examples of the polyvalent metal salts include potassium, barium, calcium, magnesium, zinc, tin, manganese, aluminum and other polyvalent metal chlorides, sulfates, nitrates, formates, acetates, and the like. Barium chloride, calcium chloride, calcium acetate, calcium nitrate, calcium formate, magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium formate, zinc chloride, zinc sulfate, zinc nitrate, zinc formate, tin chloride, tin nitrate Manganese chloride, manganese sulfate, manganese nitrate, manganese formate, aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate and the like can be exemplified, and these can be used alone or in combination of two or more. Of these polyvalent metal salts, metal salts having high solubility in water and high valence are preferable. Further, when the counter ion of the polyvalent metal salt is a strong acid, paper yellowing after coating occurs, and therefore, calcium chloride, calcium formate, magnesium chloride, magnesium formate, and the like are preferable. Examples of the cationic polymer include, but are not limited to, cationized cellulose, cationized starch, and cationized starch.

  The cationic polymers and polyvalent metal salts listed above can be distributed on the surface of the recording paper by mixing them in the surface size liquid or by applying a separately prepared coating liquid on the surface of the paper. In the latter case, the coating solution obtained by dissolving in water may be directly applied to the recording paper (or paper), but it is generally used by mixing with a binder.

Cationic polymer contained in the recording paper surface, the content of the polyvalent metal salt, it is more preferably in the range of preferably 0.5 to 1 g / m ² in the range of 0.1-2 g / m ² .
If the content is less than 0.1 g / m ² , the reaction with the pigment or anionic polymer in the ink is weakened, resulting in a decrease in image quality, curling immediately after printing, undulation, curling after standing drying, and undulation. There is a case. When the content exceeds 2 g / m ² , the ink permeability deteriorates, and the ink drying property may deteriorate in high-speed printing.

  In the recording paper of the present invention, the CD expansion / contraction rate is preferably 0.55 or less, and more preferably 0.50 or less. When the CD expansion / contraction ratio exceeds 0.55, curling / waving tends to increase even when the technique of the present invention is used.

The “CD expansion / contraction ratio” refers to the humidity of “65% RH → 25% RH → 65% RH → 90% RH” when the recording paper is left in a constant temperature environment maintained at 23 ° C. The moisture absorption / desorption treatment is changed by 1.5 hours in the order of 3 cycles, and the dimensional change rate of the recording paper when the humidity is changed from “65% RH to 25% RH” in the third cycle, that is, relative It means a in FIG. 1 showing the relationship between the humidity change and the dimensional change rate. The dimensions of the recording paper were measured using an OH Engineering H / K type elasticity tester.
Note that the CD (direction) is a direction crossing the flow direction at the time of recording paper manufacture as described above, and when measuring the dimensions of the recording paper, the dimensions in the direction crossing the flow direction at the time of recording paper manufacture were measured. .

  The recording paper of the present invention preferably has a formation index in the range of 20-50, more preferably in the range of 25-40. When the formation index is less than 20, uneven presence of the surfactant easily occurs from uneven formation, and uneven image transfer in the electrophotographic system easily occurs. When the formation index is 50 or more, it is necessary to strengthen the beating of the paper in order to ensure its homogeneity, and the curl in the ink jet recording method may increase.

  Here, the texture index is M / K Systems, Inc. A 3D sheet analyzer (M / K950) manufactured by (MKS) was used, the aperture of the analyzer was 1.5 mm in diameter, and measurement was performed using a micro formation tester (MFT). That is, a sample is mounted on a rotating drum in a 3D sheet analyzer, and a local basis weight difference in the sample is detected by a light source attached to the drum shaft and a photodetector attached to the outside of the drum corresponding to the light source. Measure as difference. The measurement target range at this time is set by the diameter of the diaphragm attached to the light incident part of the photodetector. Next, the light intensity difference (deviation) is amplified, A / D converted, classified into 64 photometric basis weight classes, 1000000 data are taken in one scan, and the histogram frequency for the data is obtained. obtain. Then, the highest frequency (peak value) of the histogram is divided by the number of classes having a frequency of 100 or more out of those classified into classes corresponding to a micro basis weight of 64, and the value obtained by dividing it by 1/100 is the ground index. Calculated. This texture index indicates that the greater the value, the better the texture.

In addition, when recording paper is used for electrophotographic image recording, the electrical characteristics of the paper are important. Particularly, in the present invention, surfactants and cationized materials that can change the electrical characteristics of the paper are frequently used. Depending on the combination and content, uneven image transfer may occur in the electrophotographic system.
In the present invention, the surface resistance value of at least the printing surface of the recording paper is preferably in the range of 1.0 × 10 ^{9 to} 1.0 × 10 ¹¹ Ω / □, and the volume resistivity is 1.0 × 10. It is preferable to set in the range of ^{10 to} 1.0 × 10 ¹² Ω · cm. If the surface resistance value and volume resistivity are not within the above ranges, image transfer unevenness may occur in the electrophotographic system.

The surface resistance value is more preferably in the range of 5.0 × 10 ^{9 to} 7.0 × 10 ¹⁰ Ω / □, and in the range of 5.0 × 10 ^{9 to} 2.0 × 10 ¹⁰ Ω / □. More preferably. The surface resistance value indicates the resistance of the surface formed by applying the polyvalent metal salt and / or the cationic resin. The volume resistivity is more preferably in the range of 1.3 × 10 ^{10 to} 1.6 × 10 ¹¹ Ω · cm, and 1.3 × 10 ^{10 to} 4.3 × 10 ¹⁰ Ω · cm. More preferably, it is in the range.
The surface resistance value and the volume resistivity are measured by a method based on JIS-K-6911 after storing for 24 hours under conditions of 23 ° C. and 50% RH and adjusting the humidity. .

<Image recording method>
Next, the image recording method of the present invention will be described.
The image recording method of the present invention can be applied to recording using an inkjet ink (hereinafter sometimes abbreviated as “ink”) or an electrophotographic toner (hereinafter sometimes abbreviated as “toner”). The recording paper is not particularly limited as long as the recording paper is used. However, the image recording method of the present invention is more preferably an ink jet recording method using ink in order to obtain a high-quality document.

(Inkjet recording type image recording method)
First, the ink jet recording type image recording method of the present invention (hereinafter sometimes referred to as “ink jet recording method”) will be described.
The ink jet recording method of the present invention is an ink jet recording type image recording method in which ink droplets are ejected onto a recording paper and an image is recorded on the surface of the recording paper.

  The ink is not particularly limited as long as it is a known ink containing at least a color material, but preferably contains a color material, an anionic compound, a water-soluble organic solvent and water as essential components. , Surfactants, various additives, and the like. Hereinafter, each component will be described.

-Color material-
Examples of the color material used in the ink include water-soluble dyes, organic pigments, and inorganic pigments.
In the case of black ink, those mainly composed of pigments are common, and examples of black pigments include carbon black pigments such as furnace black, lamp black, acetylene black, channel black, and the like. Raven7000, Raven5750, Raven5250, Raven5000 ULTRA II, Raven3500, Raven2000, Raven1500, Raven1250, Raven1200, Raven1190 ULTRAII, Raven1170, Raven1170, Raven1170, Raven1170 Mogul L, Black Pearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (manufactured by Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2, Color Black FW, Color Black FW2, Color Black FW2, Color Black FW2, Color Black FW2, Color Black FW Black S150, ColorBlack S160, Color Black S170, Pritex35, PritexU, Pritex Vrintex140U, Printex140V, Special Black6, Special Black5, Special4, Black4, Black4, Black4, Black4, Black4, Black4, Black4, Black4 Company, Ltd.), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like.

Although it is difficult to uniformly discuss a suitable structure of carbon black, the average primary particle size is 15 to 30 nm, the BET surface area is 70 to 300 m ² / g, and the DBP oil absorption is 0.5 to 1.0 × 10. ^-3 L / g, volatile content is preferably 0.5 to 10% by mass, and ash content is preferably 0.01 to 1.00% by mass. If carbon black outside the above range is used, the dispersed particle size in the ink may increase.

Color materials used in cyan, magenta, and yellow inks are not limited to dyes, and pigments made hydrophilic by adding a dispersant containing a hydrophilic group to hydrophobic pigments and self-dispersing pigments are also used. can do.
As the water-soluble dye, known ones or newly synthesized ones can be used. Among these, a direct dye or an acid dye that can provide a vivid color is preferable. Specifically, C.I. I. Direct Blue-1, -2, -6, -8, -22, -34, -70, -71, -76, -78, -86, -142, -199, -200, -201, -202, -203, -207, -218, -236 and 287; I. Direct Red-1, -2, -4, -8, -9, -11, -13, -20, -28, -31, -33, -37, -39, -51, -59, -62, -63, -73, -75, -80, -81, -83, -87, -90, -94, -95, -99, -101, -110 and 189; I. Direct Yellow-1, -2, -4, -8, -11, -12, -26, -27, -28, -33, -34, -41, -44, -48, -86, -87, -88, -135, -142 and 144; I. Acid Blue-1, -7, -9, -15, -22, -23, -27, -29, -40, -43, -55, -59, -62, -78, -80, -81, -90, -102, -104, -111, -185 and 254; I. Acid Red-1, -4, -8, -13, -14, -15, -18, -21, -26, -35, -37, -249 and 257; I. Acid Yellow-1, -3, -4, -7, -11, -12, -13, -14, -19, -23, -25, -34, -38, -41, -42, -44, -53, -55, -61, -71, -76 and 79; These may be used alone or in admixture of two or more.

  Examples of the cationic dye include C.I. I. Basic yellow-1, -11, -13, -19, -25, -33, -36; I. B. basic red-1, -2, -9, -12, -13, -38, -39, -92; I. Basic Blue-1, -3, -5, -9, -19, -24, -25, -26, -28 and the like.

  Specific examples of cyan pigments include C.I. I. Pigment Blue-1, C.I. I. Pigment Blue-2, C.I. I. Pigment Blue-3, C.I. I. Pigment Blue-15, C.I. I. Pigment Blue-15: 1, C.I. I. Pigment Blue-15: 3, C.I. I. PigmentBlue-15: 34, C.I. I. Pigment Blue-16, C.I. I. Pigment Blue-22, C.I. I. Pigment Blue-60 and the like.

  Specific examples of magenta pigments include C.I. I. Pigment Red-5, C.I. I. Pigment Red-7, C.I. I. Pigment Red-12, C.I. I. Pigment Red-48, C.I. I. Pigment Red-48: 1, C.I. I. Pigment Red-57, C.I. I. Pigment Red-112, C.I. I. Pigment Red-122, C.I. I. PigmentRed-123, C.I. I. Pigment Red-146, C.I. I. Pigment Red-168, C.I. I. Pigment Red-184, C.I. I. Pigment Red-202 and the like.

  Specific examples of yellow pigments include C.I. I. Pigment Yellow-1, C.I. I. Pigment Yellow-2, C.I. I. Pigment Yellow-3, C.I. I. Pigment Yellow-12, C.I. I. Pigment Yellow-13, C.I. I. Pigment Yellow-14, C.I. I. Pigment Yellow-16, C.I. I. Pigment Yellow-17, C.I. I. Pigment Yellow-73, C.I. I. Pigment Yellow-74, C.I. I. Pigment Yellow-75, C.I. I. Pigment Yellow-83, C.I. I. Pigment Yellow-93, C.I. I. Pigment Yellow-95, C.I. I. Pigment Yellow-97, C.I. I. Pigment Yellow-98, C.I. I. Pigment Yellow-114, C.I. I. Pigment Yellow-128, C.I. I. Pigment Yellow-129, C.I. I. Pigment Yellow-151, C.I. I. Pigment Yellow-154 and the like.

  The pigment that can be used in the present invention may be a pigment that can be self-dispersed in water (self-dispersing pigment). The self-dispersing pigment is a pigment that has many water-solubilizing groups on the pigment surface and can be stably dispersed without the presence of a pigment dispersant. Specifically, a self-dispersing pigment is obtained by subjecting a normal so-called pigment to surface modification treatment such as acid / base treatment, coupling agent treatment, polymer graft treatment, plasma treatment, oxidation / reduction treatment, etc. Obtainable. In addition to the pigment subjected to such surface modification treatment, as a self-dispersing pigment, cab-o-jet-200, cab-o-jet-300, IJJ-55, IJJ-253, manufactured by Cabot Corporation, Commercially available products such as IJX266, IJX-273 Orientjet Chemical Company's Microjet Black CW-1, and pigments sold by Nippon Shokubai Co., Ltd. may be used.

  The water-solubilizing group present on the surface of the self-dispersing pigment may be any of nonionic, cationic or anionic, and sulfonic acid, carboxylic acid, hydroxyl group and phosphoric acid are particularly desirable. In the case of sulfonic acid, carboxylic acid, and phosphoric acid, it can be used as it is in the free acid state, but it is preferably used as a salt with a basic compound in order to enhance water solubility.

  In this case, basic compounds include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine, triethanolamine and diisopropanol. Alcohol amines such as amines and basic compounds such as ammonia can be used. Among these, basic compounds of alkali metals such as sodium, potassium and lithium can be particularly preferably used. This is presumably because the alkali metal basic compound is a strong electrolyte and has a large effect of promoting dissociation of acidic groups.

  When a pigment is contained in the ink as a coloring material, the pigment content is preferably in the range of 0.5 to 20% by mass, and particularly preferably in the range of 2 to 10% by mass. When the pigment content is less than 0.5% by mass, the optical density may be lowered. On the other hand, if it exceeds 20% by mass, the image fixability may deteriorate.

  When the ink contains a dye as a coloring material, the dye content is preferably in the range of 0.1 to 10% by mass, more preferably in the range of 0.5 to 8% by mass, and still more preferably in the range of 0.8 to 6% by mass. % Range. If it is contained in an amount of more than 10% by mass, clogging at the front end of the print head is likely to occur, and if it is less than 0.1% by mass, a sufficient image density may not be obtained.

-Anionic compounds-
Examples of the anionic compound used in the ink include acids such as carboxylic acids and sulfonic acids and derivatives thereof, anionic water-soluble polymers, anionic polymer emulsions, and the like. It may be a dispersant.
Specific examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, tartaric acid, benzoic acid, acrylic acid, crotonic acid, butenoic acid, methacrylic acid, tiglic acid, allylic acid, 2- Examples thereof include carboxylic acids such as ethyl-2-butenoic acid, succinic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, methylmaleic acid and glyceric acid, and polymers and derivatives thereof. In addition, alkali metal salts, alkaline earth metal salts, ammonium salts, and the like of these compounds can also be used.

  Specific examples of the sulfonic acid include benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, benzenedisulfonic acid, benzenetrisulfonic acid, hydroxybenzenesulfonic acid, chlorobenzenesulfonic acid, bromobenzenesulfonic acid, 4-hydroxy-1 , 3-benzenedisulfonic acid, 4,5-dihydroxybenzene-1,3-disulfonic acid sodium salt, o-aminobenzenesulfonic acid and other sulfonic acids, and derivatives thereof, and alkali metal salts and alkaline earth metals thereof Examples thereof include salts and ammonium salts.

  These compounds are preferably used in the form of a salt with a basic compound in order to enhance water solubility. The compounds that form salts with these compounds include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine and triethanolamine. Alcohol amines such as diisopropanolamine, ammonia and the like can be used.

  More preferred specific examples of the anionic water-soluble polymer include acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer. Acid copolymer, styrene-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, Examples thereof include styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymers, and salts and derivatives of these copolymers.

The anionic water-soluble polymer contained in the ink preferably has a structure composed of a hydrophilic part and a hydrophobic part. Further, a carboxylic acid or a carboxylic acid salt is used as a functional group constituting the hydrophilic part. It is preferable to include.
Specifically, as the anionic water-soluble polymer, the monomer constituting the hydrophilic portion is preferably at least one selected from acrylic acid, methacrylic acid and (anhydrous) maleic acid.

  On the other hand, as monomers constituting the hydrophobic part of the anionic water-soluble polymer, styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylate esters, Examples include methacrylic acid alkyl ester, methacrylic acid phenyl ester, methacrylic acid cycloalkyl ester, crotonic acid alkyl ester, itaconic acid dialkyl ester, maleic acid dialkyl ester, among them, styrene, alkyl of (meth) acrylic acid, It is preferably at least one selected from aryl and alkylaryl esters.

  These anionic water-soluble polymers may be used alone or in combination of two or more. The content of the anionic water-soluble polymer in the ink is preferably in the range of 0.1 to 10% by mass, particularly in the range of 0.3 to 5% by mass. If the amount is less than 0.1% by mass, the long-term storage stability may be inferior, or the optical density may be reduced.

-Water-soluble organic solvent-
Examples of the water-soluble organic solvent used in the ink include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerin, Polyhydric alcohol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, pyrrolidone, N- Methyl-2-pyrrolidone, cyclohexyl pyrrolidone, triethanolamine Nitrogen-containing solvents, alcohols such as ethanol and isopropyl alcohol, butyl alcohol, benzyl alcohol, thiodiethanol, thiodiglycerol, sulfolane, sulfur-containing solvents such as dimethyl sulfoxide, propylene carbonate, ethylene and the like carbonates. The water-soluble organic solvent may be used alone or in combination of two or more.

  The content of the water-soluble organic solvent contained in the ink is preferably in the range of 1 to 60% by mass, particularly in the range of 5 to 40% by mass. If the content of the water-soluble organic solvent is less than 1% by mass, the long-term storage stability may be inferior. Moreover, when it exceeds 60 mass%, discharge stability may fall and it may not discharge normally.

-Water-
As the water used in the ink, ion exchange water, distilled water, pure water, ultrapure water, or the like can be used.
The content of water contained in the ink is preferably in the range of 15 to 98% by mass, particularly in the range of 45 to 90% by mass. If it is less than 15% by mass, the ejection stability may be lowered, and the ejection may not be performed normally. Moreover, when it exceeds 98 mass%, it may be inferior in long-term storage stability.

-Other ingredients-
A pigment dispersant can be used for dispersing the pigment contained in the ink. Specific examples of the pigment dispersant include a polymer dispersant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant nonionic surfactant, and the like.
Among these pigment dispersants, a pigment dispersant that becomes an organic anion when ionized in water is referred to as an anionic pigment dispersant in the present invention. As the anionic pigment dispersant, the anionic water-soluble polymer described above can be used.

As the polymer dispersant, any polymer having a hydrophilic structure portion and a hydrophobic structure portion can be used effectively. Examples of the polymer having a hydrophilic structure portion and a hydrophobic structure portion include a condensation polymer and an addition polymer.
Examples of the condensation polymer include known polyester dispersants. Examples of the addition polymer include addition polymers of monomers having an α, β-ethylenically unsaturated group. By subjecting a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group to appropriate copolymerization, a desired polymer dispersant is obtained. Can be obtained. A homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group can also be used.

  Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophilic group include monomers having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphoric acid group, such as acrylic acid, methacrylic acid, crotonic acid, Itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacryloxy Examples thereof include ethyl phosphate, methacrylooxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate.

  On the other hand, examples of monomers having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylates. Examples include esters, acrylic acid phenyl esters, methacrylic acid alkyl esters, methacrylic acid phenyl esters, methacrylic acid cycloalkyl esters, crotonic acid alkyl esters, itaconic acid dialkyl esters, and maleic acid dialkyl esters.

  Examples of preferred copolymers of these monomers include styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene-maleic acid. Acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-alkyl methacrylate Examples include ester-methacrylic acid copolymer, styrene-alkyl acrylate ester-acrylic acid copolymer, styrene-phenyl methacrylate-methacrylic acid copolymer, and styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer. .

  These polymers can also be used by appropriately copolymerizing monomers having a polyoxyethylene group and a hydroxyl group. Furthermore, in order to increase the affinity with the pigment having an acidic functional group on the surface and improve the dispersion stability, a monomer having a cationic functional group, such as N, N-dimethylaminoethyl methacrylate, N, N-dimethyl, etc. Aminoethyl acrylate, N, N-dimethylaminomethacrylamide, N, N-dimethylaminoacrylamide, N-vinylpyrrole, N-vinylpyridine, N-vinylpyrrolidone, N-vinylimidazole, and the like may be appropriately copolymerized and used. it can.

These copolymers may have any structure such as random, block, and graft copolymers. Polystyrene sulfonic acid, polyacrylic acid, polymethacrylic acid, polyvinyl sulfonic acid, polyalginic acid, polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer, formalin condensate of naphthalene sulfonic acid, polyvinyl pyrrolidone, polyethyleneimine, polyamine , Polyamides, polyvinyl imidazoline, aminoalkyl acrylate D acrylamide copolymer, chitosan, polyoxyethylene fatty acid amide, polyvinyl alcohol, polyacrylamide, carboxymethylcellulose, carboxyethylcellulose and other cellulose derivatives, polysaccharides and their derivatives are also used can do.
Although not particularly limited, the hydrophilic group of the pigment dispersant is preferably a carboxylic acid or a carboxylic acid salt.

The neutralizing amount of the pigment dispersant is preferably 50% or more, and particularly preferably 80% or more, with respect to the acid value of the copolymer. The pigment dispersant has a mass average molecular weight (Mw) of 2000 to 15000, and particularly preferably 3500 to 10,000. Moreover, the structure and composition rate of a hydrophobic part and a hydrophilic part can use a preferable thing from the combination of a pigment and a solvent.
These pigment dispersants may be used alone or in combination of two or more. The amount of pigment dispersant added varies greatly depending on the pigment, so it cannot be said unconditionally. However, it is generally in the range of 0.1 to 100% by weight, preferably in the range of 1 to 70% by weight, based on the pigment. Preferably it is the quantity of the range of 3-50 mass%.

The ink may contain a surfactant. This is because the pigment dispersant of the pigment ink and the surface tension and wettability of the ink are adjusted, or the organic impurities are solubilized and the reliability when ejected from the ink nozzle is improved.
As the type of the surfactant, nonionic and anionic surfactants that do not easily affect the dispersion state of the water-insoluble colorant or the dissolved state of the water-soluble dye are preferable. Nonionic surfactants include, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan Fatty acid esters, fatty acid alkylolamides, acetylene alcohol ethylene oxide adducts, polyethylene glycol polypropylene glycol block copolymers, glycerin ester polyoxyethylene ethers, sorbitol ester polyoxyethylene ethers, and the like can be used. Examples of anionic surfactants include alkylbenzene sulfonates, alkylphenyl sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, sulfates and sulfonates of higher fatty acid esters, and higher alkyl sulfosuccinates. Can be used.

  Further, as the amphoteric surfactant, betaine, sulfobetaine, sulfate betaine, imidazoline and the like can be used. In addition, silicone surfactants such as polysiloxane polyoxyethylene adducts, fluorine surfactants such as oxyethylene perfluoroalkyl ether, biosurfactants such as splicrisporic acid, rhamnolipid, and lysolecithin can also be used. The surfactant used in the ink may be used alone or in combination of two or more. What is necessary is just to adjust the addition amount by target characteristics, such as surface tension.

  Further, the ink may include a pH buffer, an antioxidant, an antifungal agent, a viscosity modifier, a conductive agent, an ultraviolet absorber, a chelating agent, a water-soluble dye, a disperse dye, an oil-soluble dye, etc. Can also be added. The content of these additives in the ink is preferably 20% by mass or less.

The ink as described above is obtained by adding a predetermined amount of a coloring material to an aqueous solution, stirring sufficiently, then dispersing using a disperser, removing coarse particles by centrifugation or the like, It can be obtained by adding an additive or the like and stirring and mixing, followed by filtration.
A commercially available dispersing machine can be used. For example, colloid mill, flow jet mill, slasher mill, high speed disperser, ball mill, attritor, sand mill, sand grinder, ultra fine mill, Eiger motor mill, dyno mill, pearl mill, agitator mill, cobol mill, 3 rolls, 2 rolls Examples thereof include a roll, an extruder, a kneader, a microfluidizer, a laboratory homogenizer, and an ultrasonic homogenizer. These may be used alone or in combination of two or more. In order to prevent mixing of inorganic impurities, it is preferable to use a dispersion method that does not use a dispersion medium. In that case, it is preferable to use a microfluidizer, an ultrasonic homogenizer, or the like.

  The ink using the self-dispersing pigment is obtained by, for example, subjecting the pigment to a surface modification treatment, adding the obtained pigment to water, stirring sufficiently, and using a disperser similar to the above as necessary. After dispersing and removing coarse particles by centrifugation or the like, a predetermined solvent, additives and the like are added, followed by stirring, mixing, and filtration.

  The pH of the ink is preferably in the range of 3 to 11, and particularly preferably in the range of 4.5 to 9.5. In addition, in an ink having an anionic free radical on the pigment surface, the pH of the ink is preferably in the range of 6 to 11, more preferably in the range of 6 to 9.5, and 7.5 to 9. A range of 0 is more preferable. On the other hand, in the ink having a cationic free radical on the pigment surface, the pH of the ink is preferably in the range of 4.5 to 8.0, and more preferably in the range of 4.5 to 7.0.

  The viscosity of the ink is preferably in the range of 1.5 to 5.0 mPa · s, and more preferably in the range of 1.5 to 4.0 mPa · s. When the viscosity of the ink is larger than 5.0 mPa · s, since the permeability to the recording paper is slow, mixed color bleeding may occur. On the other hand, when the viscosity of the ink is smaller than 1.5 mPa · s, the permeability to the recording paper is too fast, the ink pigment and the anionic compound cannot be aggregated, and the ink penetrates into the recording paper. Therefore, there is a case where the density is reduced and the characters are blurred.

  The surface tension of the ink can be adjusted mainly by the amount of the surfactant added, and is preferably adjusted in the range of 25 to 37 mN / m. When the surface tension is less than 25 mN / m, the ink permeability to the recording paper is too fast, the ink coloring material and the anionic water-soluble polymer cannot be aggregated, and the ink penetrates into the recording paper. , A decrease in density and blurring of characters may occur. On the other hand, if it is larger than 37 mN / m, the ink permeability to the recording paper becomes slow, and the drying property may be deteriorated.

When printing on the recording paper of the present invention by the ink jet method using the ink as described above, the ink drop amount ejected from the nozzle is preferably in the range of 1 to 20 pl, More preferably, it is in the range of 18 pl.
In addition, printing is performed by so-called thermal ink jet method in which droplets are formed by applying thermal energy, and the ink drop amount is in the range of 1 to 20 pl, preferably in the range of 3 to 18 pl as described above. In this case, it is preferable that the dispersed particle diameter of the pigment in the ink is in the range of 20 to 120 nm in terms of volume average particle diameter, and the number of coarse particles of 500 nm or more is 5 × 10 ⁵ or less in 2 μl of ink. . If the volume average particle diameter is less than 20 nm, sufficient image density may not be obtained. On the other hand, if the volume average particle size is larger than 120 nm, clogging is likely to occur in the print head, and stable ejection properties cannot be ensured. Further, if the number of coarse particles having a volume average particle size of 500 nm or more exceeds 5 × 10 ^{5 in} 2 μl of ink, clogging is likely to occur in the print head, and ink may not be ejected stably. The number of coarse particles is more preferably 3 × 10 ⁵ or less, and further preferably 2 × 10 ⁵ or less.

The storage elastic modulus of the ink at 24 ° C. is particularly preferably in the range of 5 × 10 ⁻⁴ to 1 × 10 ⁻² Pa. This is because by having appropriate elasticity in this region, the behavior on the surface of the recording paper becomes preferable. In addition, the said storage elastic modulus is a value when it measures in the low shear rate area | region in the range whose angular velocity is 1-10 rad / s. This value can be easily measured by using an apparatus capable of measuring viscoelasticity in the low shear rate region. Examples of the measuring device include a VE type viscoelasticity analyzer (manufactured by VILASTIC SCIENTIFIC INC.), A DCR very low viscosity viscoelasticity measuring device (manufactured by Paar Physica), and the like.

  As long as the inkjet recording method in the present invention is a known inkjet apparatus, good print quality can be obtained regardless of which inkjet recording method is used. Furthermore, for a system having a function of promoting the absorption and fixing of ink by providing heating means such as recording paper during printing or before and after printing, and heating the recording paper and ink at a temperature of 50 ° C. to 200 ° C. Also, the ink jet recording method of the present invention can be applied.

  Next, an example of an ink jet recording apparatus suitable for carrying out the ink jet recording method of the present invention will be described. This example is a so-called multi-pass method, in which an image is formed by a recording head scanning the surface of a recording sheet a plurality of times.

  As a method of ejecting ink from the nozzle, first, a so-called thermal ink jet method in which the ink in the nozzle is foamed by energizing and heating a heater provided in the nozzle, and the ink is ejected by the pressure thereof. There is also a system in which the piezoelectric element is physically deformed by energizing the piezoelectric element, and ink is ejected from the nozzles using a force generated by the deformation. A typical example of this method is one using a piezoelectric element as a piezoelectric element. In the ink jet recording apparatus used in the ink jet recording method of the present invention, the method for ejecting ink from the nozzles may be any of the above methods, and is not limited to these methods. This is the same in the following.

  The nozzles are arranged in a direction substantially perpendicular to the main scanning direction of the head carriage. Specifically, they can be arranged in a row at a density of 800 per inch. The number and density of the nozzles are arbitrary. Moreover, it can arrange not only in a line but also in a staggered pattern.

  On the upper part of the recording head, ink tanks containing the inks used in the present invention of cyan, magenta, yellow and black are integrally attached to the respective recording heads. The ink stored in the ink tank is supplied to the recording head corresponding to each color. The ink tank and the head may be formed integrally. However, the present invention is not limited to this method. For example, an ink tank may be disposed separately from the recording head and ink may be supplied to the recording head via an ink supply tube.

  Further, a signal cable is connected to each of these recording heads. This signal cable transmits image information after being processed by the pixel processing unit to each recording head for each color of cyan, magenta, yellow, and black.

  The recording head is fixed to a head carriage. The head carriage is slidably attached in the main scanning direction along the guide rod and the carriage guide. By rotating the drive motor at a predetermined timing, the head carriage can be driven to reciprocate along the main scanning direction via the timing belt.

  A platen is fixed below the head carriage, and the recording paper used in the present invention is conveyed onto the platen at a predetermined timing by a paper feed conveyance roller. The platen can be made of, for example, a plastic molding material.

  In this way, it is possible to print on the recording paper of the present invention using the ink as described above. In the example of the multi-pass method, the example in which five heads including the pretreatment liquid are provided has been described. However, the range in which the ink jet recording method of the present invention can be applied to the multi-pass method is not limited to this example. There are a total of two heads, a black head and a color head. Of these, the color head is such that the nozzles are divided in the arrangement direction and a predetermined color is assigned to each divided area. Good.

  In the so-called multi-pass method in which the print head travels perpendicularly to the recording paper discharge direction, the print head scanning speed is the speed of the recording head when the recording head performs printing by scanning the surface of the recording paper a plurality of times. Refers to moving speed.

  When performing high-speed printing with a printing speed of 10 ppm (10 sheets / min) or more, comparable to a laser printer in the office, it is inevitable that the scanning speed of the print head is 25 cm / second or more. Therefore, the interval at which two different colors of ink are printed is also narrowed, and intercolor bleeding (ICB) is likely to occur. In addition, it is necessary to use an ink having a low surface tension in order to improve the drying property of the ink, which causes the occurrence of feathering and a decrease in image density. Such an ink having a low surface tension has a high permeability to paper. Therefore, printed characters and images are easily seen through from the back side, and the double-sided printing property is impaired.

  Next, a second example of an ink jet recording apparatus suitable for carrying out the ink jet recording method of the present invention will be described. This example is called a one-pass method. This one-pass method has a recording head having a width substantially equal to the width of the recording paper, and printing is terminated when the recording paper passes under the head. Since high productivity can be obtained at the same scanning speed as compared with the multi-pass method, high-speed printing more than the laser recording method is possible.

  Since the one-pass method does not need to scan the recording head a plurality of times unlike the multi-pass method, even at a recording paper conveyance speed of 60 mm / second or more (speed at which the recording paper passes below the recording head) corresponding to 10 ppm or more, High-speed printing can be easily performed. However, since division printing cannot be performed, it is necessary to eject a large amount of ink at a time. For this reason, in the conventional inkjet recording method that does not use the recording paper of the present invention, curling and undulation immediately after printing, and further, curling and undulation after standing drying occurred.

  However, in the ink jet recording method of the present invention, the print head scanning speed in the multi-pass method is high-speed printing of 250 mm / sec or more, and the recording paper conveyance speed in a state where the print head in the multi-pass method is fixed is 60 mm. Even when high-speed printing at a speed of at least / sec is performed, the occurrence of curling and undulation of the recording paper can be suppressed by using the recording paper of the present invention described above.

  The scanning speed of the print head is preferably 500 mm / second or more, and more preferably 1000 mm / second or more, from the viewpoint of “productivity comparable to a laser printer”. Further, the conveyance speed of the recording paper is preferably 100 mm / second or more, and more preferably 210 mm / second or more.

Furthermore, in the ink jet recording method of the present invention, it is preferable that the ink shot amount is in the range of 6 to 30 ml / m ² .
The ink ejection amount is the amount of ink per unit area ejected in one scan when a solid image is formed using one or more colors of ink.

In any of the above-described methods, since ink sufficient to form a solid image with a small number of scans is applied to the recording paper, the ink ejection amount becomes as large as 6 ml / m ² or more. However, even with high-speed printing that requires such a large amount of ink, the use of the ink jet recording method of the present invention can suppress the occurrence of curling and undulations on the recording paper after printing.
Incidentally, it is preferable that the ink ejection amount is in the range of 7~20ml / m ^2, and particularly preferably more preferably within a range of 7.5~10ml / m ^2, is less than 10 ml / m ^2.

(Electrophotographic image recording method)
The electrophotographic image recording method of the present invention comprises a charging step for charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and the static step. Developing the electrostatic latent image formed on the surface of the electrostatic latent image carrier using an electrostatic latent image developer to form a toner image; and transferring the toner image to the surface of the recording paper; And a fixing step of fixing the toner image on the surface of the recording paper, wherein the recording paper is the recording paper of the present invention described above.
The electrophotographic image recording method of the present invention can obtain a high-quality image as in the conventional case and can suppress curling that occurs immediately after printing.

  The image forming apparatus used in the electrophotographic image recording method of the present invention is not particularly limited as long as it uses an electrophotographic system having the charging step, the exposure step, the development step, the transfer step, and the fixing step. . For example, when four color toners of cyan, magenta, yellow, and black are used, a four-cycle development system in which a developer containing each color toner is sequentially applied to one photoreceptor to form a toner image. Or a color image forming apparatus (so-called tandem machine) provided with four developing units corresponding to each color can be used.

  The toner used for image formation is not particularly limited as long as it is a known toner. For example, in order to obtain a highly accurate image, a spherical toner having a small particle size and particle size distribution is used, and energy saving is supported. In addition, a toner containing a binder resin having a low melting point that can be fixed at a low temperature can be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, of course, this invention is not limited to these Examples. First, after describing the ink and recording paper used in the examples and comparative examples, various evaluation results when these are combined and printed are described.

(1) Preparation of ink As ink, dye-based ink set 1 and pigment-based ink set 2 were prepared. The physical properties of the following ink were measured under the following conditions. The surface tension was measured using a Wilhelmy type surface tension meter in an environment of 23 ° C. and 55% RH. The viscosity was measured under the conditions of measurement temperature: 23 ° C. and shear rate: 1400 s ⁻¹ by placing the ink to be measured in a measurement container and mounting it on Neomat 115 (manufactured by Contraves).

<Ink set 1 (color dye ink)>
-Magenta ink-
Direct Red 227 (10% by mass aqueous solution): 20 parts by mass Ethylene glycol: 25 parts by mass Urea: 5 parts by mass Surfactant (Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 2 parts by mass Deionized water was added to bring the total amount to 100 parts by mass, and the mixture was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 31 mN / m and a viscosity of 2.0 mPa · s.

-Cyan ink-
Direct Blue 142 (10% by mass aqueous solution): 20 parts by mass Ethylene glycol: 25 parts by mass Urea: 5 parts by mass Surfactant (Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 2 parts by mass Deionized water was added to bring the total amount to 100 parts by mass and stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 31 mN / m and a viscosity of 2.0 mPa · s.

-Yellow ink-
Direct yellow 144 (10% by mass aqueous solution): 20 parts by mass Ethylene glycol: 25 parts by mass Urea: 5 parts by mass Surfactant (Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 2 parts by mass Deionized water was added to bring the total amount to 100 parts by mass, and the mixture was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 31 mN / m and a viscosity of 2.0 mPa · s.

<Ink set 2 (pigment ink)>
-Black ink-
-Surface treatment pigment (Cab-o-jet-300, manufactured by Cabot Corporation): 4 parts by mass-Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass-Diethylene glycol: 20 parts by mass-Surfactant ( Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 32 mN / m and a viscosity of 2.8 mPa · s.

-Cyan ink-
Surface treatment pigment (IJX-253, manufactured by Cabot Corporation): 4 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465, Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 32 mN / m and a viscosity of 2.5 mPa · s.

-Magenta ink-
Surface treatment pigment (IJX-266, manufactured by Cabot Corporation): 4 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465, Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 33 mN / m and a viscosity of 2.7 mPa · s.

-Yellow ink-
Surface treatment pigment (IJX-273, manufactured by Cabot Corporation): 4 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465, Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 33 mN / m and a viscosity of 2.7 mPa · s.

(2) Production of recording paper The following recording papers (1) to (24) were produced as the recording paper.
<Recording paper (1)>
Dry pulp made of hardwood kraft pulp, which was beaten and adjusted to a freeness of 420 ml, was disaggregated, and a pulp dispersion was adjusted so that the pulp solid content was 0.3% by mass.
In this pulp dispersion, 0.3 mass of succinic anhydride (ASA) internal sizing agent (manufactured by Nippon SC Co., Ltd., Fibran-81) is added to 100 parts by mass of the pulp solid content contained in the pulp dispersion. Part and 0.5 parts by mass of cationized starch (manufactured by Nippon SC Co., Ltd., Cato-304), and using an 80-mesh wire with an orientation paper machine for experiments made by Kumagai Riki Co., Ltd. Paper was made under the conditions of min and paper discharge pressure of 1.5 kg / cm ² . Then, after pressing the set for 3 minutes at 10 kg / cm ² with a press for a square sheet machine manufactured by Kumagai Riki, the set was dried at 110 ° C. and 0.5 m / min with a KRK rotary dryer manufactured by Kumagai Riki, A base paper having a basis weight of 68 g / m ² was obtained.

To this base paper, 22.5 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (Kuraray Co., Ltd., PVA102, degree of saponification: 99) , Polymerization degree: 200, contact angle with water: 64 degrees 22.5 parts by mass, nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfinol 440, HLB: 8) 40 parts by mass, carbonic acid 5 mass% aqueous solution (surface sizing liquid) containing 15 parts by mass of zirconium ammonium (Clariant Japan Co., Ltd., Cartabond), so that the processing amount to the base paper is 2 g / m ² (interface) active agent application amount is 0.8 g / m ^2, ammonium zirconium carbonate deposition volume is 0.3 g / m ^2), after size press in Kumagaya size press Riki made tests, bear 110 ° C. In physical machine made KRK rotary dryer and dried at 0.5 m / min conditions, basis weight was obtained recording paper 70g / m ² (1).

<Recording paper (2)>
Preparation of the recording paper (1) except that EMALEX GMS-B (manufactured by Nippon Emulsion Co., Ltd., HLB: 6) was used instead of Surfynol 440 which is a nonionic surfactant. Similarly, a recording paper (2) having a basis weight of 70 g / m ² was obtained.

<Recording paper (3)>
In the production of the recording paper (1), the production of the recording paper (1) was performed except that EMALEX SPIS-100 (manufactured by Nippon Emulsion Co., Ltd., HLB: 10) was used instead of Surfynol 440 which is a nonionic surfactant. Similarly, a recording paper (3) having a basis weight of 70 g / m ² was obtained.

<Recording paper (4)>
In the production of the recording paper (1), the surface sizing solution was prepared by using 12.5 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (stock) Manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) 12.5 parts by mass, monoglycidyl ether (Epiol BE-200 manufactured by NOF Corporation), 60 parts by mass, The basis weight is the same as that for the preparation of the recording paper (1) except that the aqueous solution (surface size liquid) has a concentration of 5% by mass containing 15 parts by mass of ammonium zirconium carbonate (Clariant Japan Co., Ltd., Cartabond). A recording paper (4) having a weight of 70 g / m ² was obtained.

<Recording paper (5)>
In the production of the recording paper (1), the surface sizing solution was obtained by adding 75 masses of polyvinyl alcohol as a surface sizing agent (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees). 5 mass% aqueous solution containing 10 parts by mass of monoglycidyl ether (manufactured by NOF Corporation, Epiol BE-200) and 15 parts by mass of ammonium zirconium carbonate (manufactured by Clariant Japan Co., Ltd., Cartabond) ( A recording paper (5) having a basis weight of 70 g / m ² was obtained in the same manner as in the preparation of the recording paper (1) except that the surface size liquid was changed.

<Recording paper (6)>
In the preparation of the recording paper (1), the surface sizing solution was prepared by using 30 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (Kuraray Co., Ltd.). Manufactured by PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) and nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) It is changed to a 5% by weight aqueous solution (surface size liquid) containing 10 parts by weight and 30 parts by weight of ammonium zirconium carbonate (manufactured by Clariant Japan Co., Ltd., Cartabond), and the throughput to the base paper is 1 g / m ^2. such that the (surface-active agent deposition amount 0.1 g / m ^2, ammonium zirconium carbonate deposition volume is 0.3 g / m ^2), except for changing the recording sheet (1) Ltd. and in the same manner, the basis weight was obtained recording paper 69g / m ² (6).

<Recording paper (7)>
In the production of the recording paper (1), the surface sizing solution was prepared by using 12.5 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (stock) Manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees, 12.5 parts by mass, nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) Similar to the production of the recording paper (1) except that it was changed to an aqueous solution having a concentration of 5% by mass containing 60 parts by mass and 15 parts by mass of ammonium zirconium carbonate (Cartabond manufactured by Clariant Japan Co., Ltd.). A recording paper (7) having a basis weight of 70 g / m ² was obtained.

<Recording paper (8)>
In the preparation of the recording paper (1), the surface sizing solution was obtained by using 17.5 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (stock) 17.5 parts by mass of Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees, nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) 5 mass parts including 20 mass parts, 30 mass parts of monoglycidyl ether (Nippon Yushi Co., Ltd. Epiol BE-200), and 15 mass parts of zirconium carbonate ammonium (Clariant Japan Co., Ltd., Cartabond). % change in aqueous solution having a concentration (surface sizing solution), except that the amount of processing into the base paper was changed to be 2 g / m ² recording paper (1) Ltd. and in the same manner, the basis weight was obtained recording paper 70g / m ² (8).

<Recording paper (9)>
In the production of the recording paper (1), the surface sizing solution was prepared by using 10 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent, and polyvinyl alcohol (Kuraray Co., Ltd.). Made by PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) and nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) The basis weight of the recording paper (1) is the same as that of the recording paper (1) except that the aqueous solution has a concentration of 5% by mass including 40 parts by mass and 40 parts by mass of ammonium zirconium carbonate (Cartabond manufactured by Clariant Japan Co., Ltd.). A recording paper (9) of 70 g / m ² was obtained.

<Recording paper (10)>
In the production of the recording paper (9), the basis weight is the same as the production of the recording paper (9) except that polycarbodiimide (Nihonshinbo Co., Ltd., Carbodilite V-02-L2) is used instead of ammonium zirconium carbonate. A recording paper (10) of 70 g / m ² was obtained.

<Recording paper (11)>
In the production of the recording paper (9), the basis weight is the same as the production of the recording paper (9) except that polyglycidyl ether (Nippon Yushi Co., Ltd., Epiol E-1000) is used instead of ammonium zirconium carbonate. A recording paper (11) of 70 g / m ² was obtained.

<Recording paper (12)>
In the production of the recording paper (1), the surface sizing solution was prepared by using 40 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent, and polyvinyl alcohol (Kuraray Co., Ltd.). Manufactured by PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) and 40 parts by weight of a nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) 10 parts by mass and 10 parts by mass of ammonium zirconium carbonate (Clariant Japan Co., Ltd. Cartabond) were changed to an aqueous solution (surface sizing liquid) having a concentration of 5% by mass, and the throughput to the base paper was 1 g / m ² . action of such that (surfactant application amount is 0.1 g / m ^2, ammonium zirconium carbonate deposition volume is 0.1 g / m ^2), except for changing the recording sheet (1) In the same manner as, the basis weight was obtained recording paper 69g / m ² (12).

<Recording paper (13)>
In the production of the recording paper (1), the surface sizing solution was prepared by adding 48 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (Kuraray Co., Ltd.). 48 parts by mass, PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees, and nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) 3 parts by mass and 1 part by mass of ammonium zirconium carbonate (Clariant Japan Co., Ltd. Cartabond) were changed to an aqueous solution (surface size liquid) having a concentration of 5% by mass, and the amount of processing on the base paper was 1 g / m ² . action of such that (surfactant applied amount is 0.01 g / m ^2, ammonium zirconium carbonate deposition volume is 0.01 g / m ^2), except for changing the recording sheet (1) In the same manner as, the basis weight was obtained recording paper 69g / m ² (13).

<Recording paper (14)>
In the production of the recording paper (1), the surface sizing solution was prepared by using 10 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent, and polyvinyl alcohol (Kuraray Co., Ltd.). Made by PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) and nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) The amount is changed to a 5% by weight aqueous solution (surface size liquid) containing 80 parts by mass and 0.5 parts by mass of ammonium zirconium carbonate (manufactured by Clariant Japan Co., Ltd., Cartabond). so that 5 g / m ² (surface active agent deposition amount 2.0 g / m ^2, ammonium zirconium carbonate deposition volume is 0.02 g / m ²⁾ recording paper was changed 1) Preparation and in the same basis weight to obtain a recording paper of 71g / m ² (14).

<Recording paper (15)>
In the production of the recording paper (13), in the same manner as in the production of the recording paper (13), monoglycidyl ether (manufactured by NOF Corporation, Epiol BE-200) was used instead of the nonionic surfactant. A recording paper (15) having an amount of 69 g / m ² was obtained.

<Recording paper (16)>
In the production of the recording paper (14), in the same manner as in the production of the recording paper (14) except that monoglycidyl ether (Nippon Yushi Co., Ltd., Epiol BE-200) was used in place of the nonionic surfactant. A recording paper (16) having an amount of 69 g / m ² was obtained.

<Recording paper (17)>
In the production of the recording paper (1), the surface sizing solution is changed to a 27% by weight aqueous solution (surface sizing solution) containing only zirconium ammonium carbonate (manufactured by Clariant Japan Co., Ltd., Cartabond). There except that (is zirconium ammonium carbonate applied amount 3.2 g / m ²⁾ so that the 3.2 g / m ² was changed in the same manner as in the preparation of the recording paper (1), recording a basis weight of 71 g / m ² A paper (17) was obtained.

<Recording paper (18)>
In the production of the recording paper (1), the surface sizing liquid is converted into a 5% by weight aqueous solution (surface sizing liquid) containing only a nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX RWL-150, HLB: 12). In the same manner as in the preparation of the recording paper (1) except that the amount was changed so that the processing amount to the base paper was 2.5 g / m ² (the amount of surfactant applied was 2.5 g / m ² ) A recording paper (18) having an amount of 71 g / m ² was obtained.

<Recording paper (19)>
In the production of the recording paper (1), the surface sizing solution was prepared by using 15 parts by mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent and polyvinyl alcohol (Kuraray Co., Ltd.). Manufactured by PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) and nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX RWL-150, HLB: 12) 40 And an aqueous solution (surface size liquid) having a concentration of 5% by mass including the mass part, so that the processing amount to the base paper becomes 1.0 g / m ² (surfactant applied amount is 0.4 g / m ^2). A recording paper (19) having a basis weight of 69 g / m ² was obtained in the same manner as in the preparation of the recording paper (1) except that the amount of zirconium carbonate added was changed to 0.3 g / m ² .

<Recording paper (20)>
Green 100 paper (medium quality recycled paper, no surface sizing agent) manufactured by Fuji Xerox Office Supply was used as the recording paper (20).

<Recording paper (21)>
Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, water-dispersed copolyester resin dispersion (Vylonal MD-1200 adjusted to 5% by mass as solid content, manufactured by Toyobo Co., Ltd.) After applying size press (coating) on both sides of the paper so that it becomes ² g / m ² by using a size press for testing by Kumagai Riki, it is dried at 140 ° C. and 0.5 m / min using a KRK rotary dryer manufactured by Kumagai Riki. As a result, a recording paper (21) having a basis weight of 70 g / m ² was obtained.

<Recording paper (22)>
Fuji Xerox Office Supply Green100 paper (medium recycled paper) and aqueous urethane resin solution (manufactured by Dainichi Seika Co., Ltd., waterborne polyurethane Resamine W W-100) with a dry weight of 2 g / m ² A size press (coating) was performed on both sides of the plate using a size press for testing by Kumagai Riki, followed by drying with a KRK rotary dryer manufactured by Kumagai Riki under the conditions of 140 ° C. and 0.5 m / min, and a basis weight of 71 g / m ² was recorded. A paper (22) was obtained.

<Recording paper (23)>
Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply is coated with an aqueous polyvinyl alcohol solution (an aqueous solution containing 1% by mass of polyvinyl alcohol PVA124 manufactured by Kuraray Co., Ltd. as a solid content), and the solid content is 5 g / m ² in dry mass. After applying size press (coating) on both sides of the paper with a size press for testing made by Kumagai Riki, the paper was dried with a KRK rotary dryer made by Kumagai Riki under the conditions of 140 ° C. and 0.5 m / min, and the basis weight was 73 g / m. ² recording sheets (23) were obtained.

<Recording paper (24)>
Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, an aqueous cationized cellulose solution (an aqueous solution containing 1% by mass of cationized cellulose manufactured by Daicel Chemical Industries, Ltd. as a solid content), and a solid content of 5 g / m in dry mass ^After pressing the size of both sides of the paper with a size press for testing by Kumagai Riki so that it becomes ² , dry it at 140 ° C and 0.5 m / min with a KRK rotary dryer made by Kumagai Riki. A recording paper (24) of 73 g / m ² was obtained.
Tables 1 and 2 collectively show the configuration and characteristic values of the above recording sheets.

(Examples 1 to 1 3 , Reference Examples 1 and 2 and Comparative Examples 1 to 10)
Using the recording paper, image recording was performed by an ink jet recording method and an electrophotographic method, and the recording paper performance was confirmed as follows. Table 3 summarizes the recording paper used in each example, reference example, and comparative example, ink jet recording conditions, and the like.

(1) Evaluation by inkjet recording method Printing evaluation is performed in an environment of 23 ° C. and 50% RH, and printing is performed using a thermal inkjet recording apparatus for evaluation of multi-pass printing including four recording heads. ink ejection nozzle pitch is 800 dpi, the ink discharge nozzles 256 nozzles, the discharge amount of about 15 pl, ink ejection amount is the standard and 10 ml / m ^2, and the two levels of 7.5 ml / m ^2. Printing was performed by single-sided batch printing at a head scan speed of about 28 cm / sec.

Various evaluations after printing were performed as follows.
-Curling evaluation immediately after printing-
A margin of 5 mm was taken on a postcard-sized recording paper, a 100% solid Magenta image was printed, and the amount of hanging curl generated immediately after printing on the surface opposite to the printed surface was measured. The measured value was converted into curvature and evaluated. The evaluation criteria are as follows, where ○ is an acceptable level.
○: 20 m ⁻¹ or more and less than 35 m ⁻¹ Δ: 35 m ⁻¹ or more and less than 50 m ⁻¹ ×: 50 m ⁻¹ or more

−Wave evaluation immediately after printing−
A 2 cm × 2 cm secondary color 100% solid (Blue) image was printed on a postcard-sized recording paper at the center of the postcard, and the maximum height of the corrugation generated immediately after printing was measured with a laser displacement meter. The evaluation criteria are as follows, where ○ is an acceptable level.
○: 1 mm or more and less than 2 mm Δ: 2 mm or more and less than 3 mm x: 3 mm or more

-Curling evaluation after leaving to dry-
5mm margin on a postcard size recording paper, printing a 100% Magenta solid image, leaving the printing surface flat on an environment of 23 ° C and 50% RH, and hanging after leaving for 100 hours after printing The amount of curling was measured. The measured value was converted into a curl curvature and evaluated. The evaluation criteria are as follows, and ○ and Δ are acceptable levels.
○: Less than 30 m ⁻¹ Δ: 30 m ⁻¹ or more and less than 75 m ⁻¹ ×: 75 m ⁻¹ or more

-Image quality evaluation-
An image in which Yellow 100% and Black 100% are adjacent to each other was printed on a postcard-sized recording paper, and the boundary was evaluated according to the following criteria. ○ is an acceptable level.
○: No blurring occurs in the mixed colors of the image, and the back surface is small.
Δ: Slight blurring of mixed colors in the image or slight offset
X: The image has mixed color bleeding or a large setback.
The above results are summarized in Table 3.

(2) Evaluation by electrophotographic method For the recording sheets (1) to (20), Fuji Xerox Printing Systems Co., Ltd. DocuPrint C3530 is used as an electrophotographic recording apparatus, and the following is performed at 22 ° C. and 55% RH environment. Was evaluated.
A margin of 5 mm was taken on a postcard-sized recording paper, printer output was performed using a Magenta 100% solid image, and toner running performance was evaluated according to the following evaluation criteria. ○ is an acceptable level.
○: There is no problem in running performance. There is no practical problem.
Δ: A paper jam occurs rarely in the machine. There are practical problems.
×: Paper jam frequently occurs in the machine. There are practical problems.

For the recording sheets (21) to (24), the following evaluation was performed using DocuCentreColor400CP manufactured by Fuji Xerox Co., Ltd. as an electrophotographic recording apparatus.
A 5 mm margin was taken on a postcard-sized recording paper, a 100% solid Magenta image was printed, and the amount of hanging curl generated immediately after printing was measured. The measured value was converted into curvature and evaluated. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
A: Less than 10 m ^{-1 B} : 10 m ^-1 or more and less than 20 m ^-1 Δ: 20 m ^-1 or more and less than 35 m ^-1 ×: 35 m ^-1 or more The results are shown in Table 3.

  As shown in Table 3, the recording paper of the present invention used in the examples was excellent in image quality with no curling or undulation after printing in both the ink jet recording method and the electrophotographic method. On the other hand, in the recording paper of the comparative example, some problems such as curling after printing, image quality deterioration, and in-machine running failure occurred.

It is a graph for demonstrating the definition of CD expansion-contraction rate in this invention.

Claims (3)

A nonionic surfactant having a HLB of 6 or more and less than 11 is selected from at least one selected from monoglycidyl ethers having at least one reactive group that reacts with a carboxyl group and an active hydrogen group of a hydroxyl group. One selected from ammonium zirconium carbonate, polycarbodiimide and polyglycidyl ether having a reactive group capable of reacting with an active hydrogen group such as a carboxyl group and a hydroxyl group, contained in the range of 05 to 1.5 g / m ² The above is contained in the range of 0.03 to 1.0 g / m ² , the water retention value C of the paper represented by the following formula (1) is in the range of 50 to 100%, and is represented by the following formula (2). The recording paper is characterized in that the wet tensile strength residual ratio R in the CD direction of the paper to be printed is in the range of 5 to 20%.
Water retention value C (%) = {(A−B) / B} × 100 Formula (1)
Residual ratio of wet tensile strength in CD direction R (%) = (Sw / S) × 100 Formula (2)
(In the above formula (1), A represents the mass (g) of the wet paper piece after centrifugal dehydration, and B represents the absolute dry mass (g) of the paper. In the above formula (2), Sw represents the wet tension. Strength (kN / m), S represents the tensile strength (kN / m) in the dry state. An inkjet recording type image recording method for discharging ink droplets onto a recording sheet and recording an image on the surface of the recording sheet,
The image recording method according to claim 1, wherein the recording sheet is the recording sheet according to claim 1.   A charging step for charging the surface of the latent electrostatic image bearing member; an exposure step for exposing the surface of the latent electrostatic image bearing member to form a latent electrostatic image; and a static electricity formed on the surface of the latent electrostatic image bearing member. Developing a latent image using an electrostatic latent image developer to form a toner image, a transferring step for transferring the toner image to the surface of the recording paper, and a fixing step for fixing the toner image on the surface of the recording paper An image recording method according to claim 1, wherein the recording paper is the recording paper according to claim 1.